Autopilot-guided farm vehicles are now considered a necessity for efficient farm operations. Autopilots drive more accurately than humans and never get tired. They improve the precision, and reduce the cost, of tilling, planting, spraying, harvesting and other tasks.
An agricultural autopilot takes over steering duties from a human operator. It may operate hydraulic control valves to actuate a steering mechanism or literally turn a steering wheel. A typical autopilot used in a farm tractor guides the tractor along a pre-programmed path by maneuvering the tractor's steerable front wheels.
Autopilot performance is degraded if the steerable wheels lose traction. This can happen when there is not enough weight on the wheels, when ground under the wheels is wet or loose, or when operating on a slope. Side hill operations can be especially irksome if a tractor keeps drifting or sliding downhill. Adding weight improves traction, but adding too much weight also causes undesirable soil compaction.
Even with good traction a tractor sometimes cannot turn as sharply as desired. As an example, tractors often cannot turn sharply enough to transition from one work row to the next in a single, smooth turn when turning around at the end of a field. Looping turn-around maneuvers (key hole turns) or backing up waste time and usable field area.
Thus, despite an autopilot's ability to steer the wheels of a tractor (or other agricultural vehicle) through their full range faster and more precisely than a human operator, an autopilot cannot guarantee that a pre-programmed path will always be followed accurately given less-than-ideal traction or mechanical steering limits. What is needed is a tractor autopilot that guides a tractor accurately despite these problems.